A generic method, in particular using an x-ray tomograph with two x-ray beam sources is known from the publication “First performance evaluation of a dual-source CT (DSCT) system” by Flohr et al., which appeared in Eur. Radiol. 2006, 16, pages 256 to 268.
By recording a first data record and a second data record of the myocardial wall in the same cardiac phase by means of x-ray radiation with differing radiation intensities, the myocardial wall is segmented by the first data record and the second data record. However a corresponding image comprises only an external outline of the myocardial wall and shows the coronary arteries.
Current studies show that cardiological diseases are constantly on the increase. There is therefore a need to identify possible pathological changes, stenoses, constrictions, etc, as early as possible. There is therefore an emphasis on segmenting the pump function of the heart and in this process principally that of the left chamber, the so-called ventricle and its myocardial wall, the myocardium. Stenosed or calcified coronary arteries, which are no longer able to supply the myocardium with sufficient oxygen-rich blood, have the greatest negative effect on this pump function. As a result the muscle of the region supplied by the corresponding coronary artery is weakened and in time ceases to play an active role in the contracting movement, thereby weakening cardiac output. During the further course of the disease fat cells accumulate specifically at these less perfused points of the myocardium.
In current standard examinations coronary protocols are used, which set the dose of an x-ray tube of a CT scanner so that it is possible to achieve an optimum contrast between the lightness of the interiors of the coronary arteries filled with contrast agent and the darkness of external tissue. This standard protocol allows a distinction between contrast agent and tissue but makes a tissue classification between the myocardium and surrounding tissue, which is of interest for cardiological applications, virtually impossible. The reason for this is a relatively high x-ray tube voltage, typically approximately 120 kV, for recording a first data record.
In current cardiological examinations, such as induced computed tomography scans—abbreviated to CT scans—an attempt is made to find pathological changes to the coronary arteries by examining the coronary arteries themselves. In other words an attempt is made to find constrictions and stenoses or calcifications by tracking each individual coronary artery in the CT data and checking for pathological changes. This method has three significant disadvantages:
Firstly this method is very time-consuming, since every individual branch of the coronary arteries would have to be tracked in CT recordings. A large number of branches of the coronary arteries means a time outlay that is no longer reasonable. To manage this time outlay, frequently only a few main branches of the coronary arteries are examined, resulting in a greatly reduced probability of discovery. In other words the pathological changes are only identified very late and not at an initial stage, thereby resulting in a lower probability of recovery and serious and extremely cost-intensive delay consequences.
Secondly pathological changes in the coronary arteries that are present in the initial stage cannot be detected on the basis of examinations of the coronary arteries themselves.